Hello Tim,
Here's some battery info which may help in the future:
http://www.phantompilots.com/threads/do-you-break-in-your-lipos-heres-how.37113/
Any chance of letting us know, generally, where you're flying? Denver @ 5,000 feet, or Miami @ 5 feet, makes a big difference. I encourage all members to add some info to their signature line, such as props, battery, mods. It's also helpful if in your profile we can see where you are.
Anyway, sounds like good info so far. I turned my gimbal bracket around as well. When 2 motors are working harder than the other 2, it really limits your capabilities.
13 minutes is **** good time. I am really curious about which battery gave you that flight.